The mechanism behind the progressive cachexia in cancer patients must relate to the fuel economy of the host. Although energy intake is generally low in cancer patients, the more rapid the weight loss associated with progressive cancer compared to self- imposed normal weight loss suggests that the negative energy balance could be ascribed to an increase in metabolic expenditure. The contribution of the energy cost of increased glucose turnover and gluconeogenesis from lactate and alanine and protein synthesis could help explain the increased metabolic rates reported and the concomitant weight loss. Although the above considerations are logical, the documentation of these increased metabolic parameters has not been consistent, possibly due to variations of tumor type and staging. It has been stated that "early" cancer is not associated with these increases. Our data in early colorectal cancer support this time-dependent response. Since the reported metabolic studies are mainly isolated ones, this project is designed to simultaneously evaluate resting energy expenditures (RME), glucose turnover and recycling, and whole- body protein synthesis and breakdown rates in a defined group of lung cancer patients. The RME measurements will be determined by the direct calorimetric method; glucose kinetics will be evaluated using a constant infusion method employing 14C-UL- glucose-3H-6-glucose; and whole-body protein synthesis and breakdown using a constant infusion of 15N-glycine. Using standard procedures, nitrogen balance will also be determined. We will correlate the energy cost of increased synthesis (recycling) of glucose and protein turnover normalized to measure lean body mass with any increased RME associated with this stage of disease. It will also be appropriate to measure other substrates and hormonal levels for possible correlations with the RME and kinetic studies. It is felt that these overall measurements in the same patient with extreme disease will provide an insight on mechanisms of weight loss in cancer patients.